Curb's "Larry David's" (as opposed to the real-life Larry David) reasoning for a reunion stunt he would otherwise deem "desperate" and "pathetic"? He wants to get back together with estranged wife Cheryl (Cheryl Hines), but she can only stand him in small doses--like when he's working. Hence, Larry whips up a new project for himself--a Seinfeld reunion! If you're now confused, Curb probably isn't for you.
Unlike Seinfeld, which was (believe it or not) scripted, the gang's interaction on Curb Your Enthusiasm is entirely improvised and, despite his absence in these two clips, Michael Richards (Kramer) is on-board and poised for a whole lotta racism gags at his expense. If you're now offended, again, Curb probably isn't for you.